Roof bows are attached to vehicle roof structures to strengthen the roof and support the roof rails. Current roof rail designs include a rail that extends transversely across the vehicle roof from one roof rail to the other roof rail and have a substantially uniform width as measured in the fore-and-aft direction. Such roof rails do not include lateral supporting reinforcements between the windshield header rail, the rail extending between the B-pillars, and the rail extending between the C-pillars.
Vehicles are subjected to Federal Motor Vehicle Safety Standards (FMVSS) tests in the United States. In FMVSS Side Pole Impact Tests a pole is impacted by the test vehicle that may engage the vehicle in a location where the roof rail is not supported by a transversely extending rail. The unsupported portion of the roof rail may allow unacceptable intrusions into the passenger compartment. Vehicles are also subjected to FMVSS Roof Crush Tests that apply an impact load to the vehicle roof in the area of the roof rail.
Improving test results in the above FMVSS tests is normally addressed by increasing the section size and the thickness of the parts of the roof rail. Increasing the section size and thickness of the roof rails adds weight to the vehicle and may reduce visibility below the roof rail. It is a current objective to reduce vehicle weight to achieve greater fuel efficiency. Any increase in weight is considered to be a problem.
The use of a K-shaped roof bow has been proposed to improve test performance that is joined to the roof rail by welds and rivets. A K-shaped roof bow joined by welds or rivets to the roof rail may separate in the test and limit the effectiveness of such a design in transferring loads from the roof rails to the K-shaped roof bow.
This disclosure is directed to addressing the above problems and other problems as summarized below.